Method of treating copper alloys and improved product



Aug. 7. l 928. 1,680,045

V. O. HOMERBERG ET AL METHOD OF TREATING COPPER ALLOYS AND IMPROVED PRODUCT Filed Jam. 28. 1926' 2 Sheets-Sheet l 5o I00 PERCENT zmc av WEIGHT Aug; 7, l 928.

v. o. HOMERBERG ET AL I METHOD OF TREATING COPPER ALLOYS AND IMPROVED PRODUCT Filed Jan. 28, 1926 2 Sheets-Sheet 2 o'eizzra,

Ems 2% Patented Aug. 7, 1928.

UNITED STATES v 1,680,045 PA'TENT. OFFICE.

VICTOR O. HOMERBERG, F BELMONT, MASSACHUSETTS, AND DEXTER N. SHAW, 0F PHILADELPHIA, PENNSYLVANIA.

METHOD OF TREATING COPPER ALLOYS AND IMPROVED PRODUCT.

Application filed January 28, 1926. Serial No. 84,386.

We have discovered a method of treating copper alloys, whereby it becomes possible to obtain products having definite predetermined characteristics of tensile strength,

a hardness or ductility, according to the result desired. The characteristic feature of our method is a double heat treatment with intermediate quenching, the first heat treatment being at a relatively high temperallu ture, while the temperature of the second heat treatment is. lower, but will vary with the characteristics desired in the finished product. Our process has been found particularly valuable for the heat treatment of la brass such as 60-40 brass or Muntz metal, but it may also be applied to other brasses, ranging from 63% to 45% copper, and it may also be applied to other copper alloys, of which the temperature composition diagram resembles that portion of the brass diagram where Muntz metal 1s found. Portions of both the copper-tin (bronze) and copper-aluminum diagrams have such resemblances.

One accepted copper-zinc temperaturecomposition diagram is shown diagrammatically in Fig. 1. The exact points of this curve are at the present time in controversy, hence this diagram is merely illustrative and not to be considered theoretically correct. 'The portion of the curve to which this 1nvention applies is approximately between 37 and 55% zinc. The portion bounded by AD and BCis known asthe beta field and is-a single solid. solution which exists in equilib rium at points above the critical temperature shown by the lines AD and BC. If an alloy in the form of the single solid solution, beta, is rapidly cooled, the beta will be obtained at room temperature. Upon reheating, at temperatures disclosed, the beta will be transformed into the structure in equilibrium at the reheating temperature. For each reheating temperature, there is a corresponding crystalline structure and corresponding physical properties. The relation of the physical properties to the reheating temperature is illustrated in Fig. 2 and will be considered below.

There may be present small percentages up to or even more of other metals, such as lead, zinc, tin, aluminum, manganese, iron, nickel, cobalt, chromium, magnesium, tungsten, or non-metallic elements such as arsenic, phosphorus, sulphur. When these materials are added intentionally, it is for the ppl rpose of improving the properties of the a 0y. The metal to be treated according to our mvention may originally have been cast, rolled drawn, extruded'or spun and it may or may not have been previously annealed. The important thing is that our first heat treatment is at such a relatively high temperature as to be above the critical temperature at which the single solid solution exists. Those alloys to which our invention is applicable normally exist at room temperature made up of two components, usually two solid solutions designated as alpha and beta; The alloys have the further property of transforming into a single solid solution called beta above a certain definite pointcalled the critical temperature. If the alloy is allowed to transform into the beta condition and then is quenched quickly. substantially a single solid solution, beta, will be obtained at room temperature. In -40 brass, for example, the critical temperature is 775 (1., or thereabouts, but it varies within limits for different alloys and for different compositlons of copper alloys. Thus in an alloy with 52% copper, the temperature mightbe as low as 550 C. For copper.

aluminum alloys, the temperatures will vary from 550 C. to 1050 C. This temperature of the critical range is dependent on the composition and can be ascertained from the known diagram.

In practlce, We have found a temperature of 825 C. for a eriod of two hours to be suitable for this rst heat treatment in the case of Muntz metal, but as the result at the end of this first treatment is in some measure a function of time and temperature,

the latter may be varied somewhat by varying the length of this treatment.

This first heat treatment is followed by a quick quenching, preferably in cold brine, but other quenching media may be used.

The metal will now be in a condition of beta microstructure as the result of rapid cooling, although alpha may be found as a fringe at the grain boundaries. A second heat treatment at temperatures which we have determined will give a product having predetermined characteristics of strength, hardness or ductility. To start with the metal in the beta condition insures that results loo which are predetermined and reproducible will be obtainedwhen the metal undergoes alloy to a temperature of over 775 C. for a length of time which. may vary from half an hour to two hours. For example, we have found that a temperature as high as 825 C. and a period of treatment as long as two hours have given good results. These factors, temperature and time, may vary, the object being to heat for a time and at a temperature which will transform the alloy into substantially a single solid solution. M

At the end of this first heat treatment, the metal is subjected to a quick quenching. Brine at a temperature of -8 C. may be used as the quenching medium. Any other medium will serve which will cause the piece to cool quickly enough to produce substantially pure beta solid solution at room temperature. The metal is now subjected to a second heat treatment, which is below that of the first heat treatment. In practice, we have found that the best results for high tensile strength are obtained when the second heat treatment is somewhere in the neighborhood of 250 C. The piece is kept at this reheating temperature until the single solid solution beta is transformed into alpha plus beta. This usually requires a shorter time than theprimary heating. We have obtained good results with a temperature of about 250 C. for thissecond heat treatment and the length of the treatment half an hour. Thereafter for the production of high tensile strength and hardness the alloy metal is cooled in any convenient way, for we have found that the rate of this final-cooling has no appreciable effect on the physical properties of the metal. This treatment will give an alloy which will be free from internal strains, a condition heretofore unknown with a brass of high tensile strength and hardness.

By the described process of double heat treatment, we have obtained the copper al- 10y, -40 brass, with the remarkably high tensile strength of 82,7 50 pounds per square vinch, with no elongation and a hardness of If it is desirable to obtain an alloy having an appreciable elongation but with a high tensile strength and hardness, temperature of 300 C. or of 350 C. may be used. The exact reheating temperature to be used to obtain the hysical properties desired is ascertainable f fom the predetermined schedule or plot. I I

Attention is called to our co-pending application Serial No. 689,504, filed January 30, 1924, of which the present case is a continuation in part. In our co-pendin case, the heat treatment to obtain alloys 0' hi h tensile strength and hardness is specifica I claimed. There are also product claims directed to new copper alloys of high tensile strength and hardness. In the present case, the claims cover the Whole range of reheating temperatures and there are also specific claims for the heat treatment to obtain alloys of high ductility.

If on the other hand, it be desired to obtain an alloy having a high ductility, the reheating temperature used is somewhat higher, that is, from 400 C. or 450 C. to 700 C. or to 750 0. depending upon the other physical characteristics accompanying the ductility that are desired.

For example, let us su pose that we wish to obtain a 60-40 brass 0 high ductility, we proceed as follows:

Let us assume that the alloy is about 60 parts copper to about 40 parts of zinc, and containing, it may be also quite small percentages, other materials, such as lead, 1ron or manganese. We first subject this alloy to a temperature of over 775 of time which may vary from half an hour to two hours. For example, we have found that a temperature as high as 825 C. and a period of treatment as long as two hours have given ood results. These factors, temperature an time, may vary, the object being to heat for a time and at a temperature which will transform the alloy into substantially a single solid solution.

At the end of this first heat treatment, the metal is subjected to a quick quenching. Brine at a temperature of 8 C. may be used as the quenching medium. Any 'other medium will serve which will cause the piece to cool quickly enough to produce substantially pure beta solid solution at room temperature. The metal is now subjected to a second heat treatment, which is below that of the first heat treatment.

In practice, we have found that the be results for high ductility are obtained when the second heat treatment is somewhere in the neighborhood of 450 C. The piece is kept at this reheating temperature until the single solid solution beta is transformed into alpha or the proportions of components, al- .pha and beta, which are in equilibrium at the reheating temperature.

C. for a length' a reheating Thisnsually requires a shorter time than the primary heating. We have obtained good results With'a temperature of 450 C. or thereabouts for this second heat treatment and the length of the treatment, half an hour. Thereafter the piece is cooled in any convenient way which will maintain the equilibrium structure at room temperature. Cold Water, oil or brine may be used. Treatment of alloys according to the process of the invention gives alloys free from internal strains.

If it bedesired to obtain an alloy with a higher tensile strength and hardness than results when a reheating temperature of 1:50" C. is used, the piece may be heated at temperatures up to the critical temperature, the exact temperature depending on the physical properties desired and being determined from a predetermined schedule, as hereinbefore discussed.

At each reheating temperature, there is an equilibrium' microstructure dependent upon the reheating temperature. This is obtained at room temperature by cooling at a rate which will not permit the structure to change. At relatively low temperatures, say below 450 (1., the piece may be cooled in the air without a change in the structure taking place. Athigher temperatures, it maybe necessary to quench the piece in order that the rate of cooling will be sufiiciently rapid to obtain the structure of the reheating temperature at room temperature. The physical properties obtained in a given piece are dependent upon the microstructure. As has hereinbetore been mentioned, the very fine uniformly distributed alpha plusbeta. gives an alloy with remarkable tensile strength and hardness while the alloy ob tained at 450 C. has a high elongation with a good tensile strength and hardness.

The following table which is graphically illustrated in the diagrammatic Fig. 2 of the accompanying drawings will serve as a guide to obtain any desired useful character of iinal product, although the temperature in any given case maybe varied slightly, especially it the normal period of half an hour for the second heat treatment be varied Table.

Brinell hardness Tensile Per cent Reheating temperature strength, elqngadegrees C. 1 lbs. tion 500 kg. 3000 kg. sq.m 1n 2 in.

From this, it is seen that with a given alloy, it becomes possible to obtain by our double'heat treatment a product with 211- most any desired physical properties from a low tensile piece with high elongation to one having high tensile strength with practically no elongation. These results are definite and can be predetermined by employing the appropriate reheating temperatures.

The figures in the accompanying table and drawing vary with the time and tcmpcratures of operation, and the composition of the alloys being treated and are to be interpreted only as examples of the broad scope of the invention. Considerable modification in these factors is possible with no departure from the essential features of the invention.

lVe claim:

1. The process of treating those copper alloys whose composition is such that the particular alloy'being treated falls within that portion of the tempcrature-composition diagram of its system which resembles the portion of the copper-zinc temperature composition diagram in which (30-40 brass is found, which comprises heating the alloy above the critical temperature to obtain substantially a single solid solution; quenching to obtain this substantially single solid solution at room temperature; and thereafter selecting a predetermined reheating temperature corresponding to the physical properties desired, heating at said chosen temperature and subsequently cooling to ob tain substantially the structure corresponding to that of the reheating temperature at room temperature.

2. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperature-composition diagram in which 60-410 brass is found, which comprises heating the alloy above the critical temperature to obtain substantially a single solid solution; quenching to obtain this substantially single solid solution at room temperature; and thereafter selecting a predetermined reheating temperature corresponding to the physical properties desired, heating at said chosen temperature and subsequently cooling to obtain substantially the structure corresponding to that of the reheating temperature at room temperature.

3. The process of treating those copper alloys Whose composition is such that the particular alloy being treated falls within that portion of the temperatur-erompositi on diagram of its system which resembles the portion of the copper-zinc temperaturecomposition diagram in which 60-40 brass is found, which comprises heating the alloy to a point above its critical temperature to obtain substantially a single solid solution; quenching to obtain substantially a single llli .order to obtain solid solution at room temperature; reheating at a temperature which will give a structure corresponding to. the properties desired; and thereafter cooling to obtain substantially this structure at room temperature.

4. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperaturc-composition diagram in which 60-40 brass is found, which comprises heating the alloy to a point above its critical temperature to obtain substantially a single solid solution; quenching to obtain substantially a single solid solution at room temperature; reheating at a temperature which will give a structure corresponding to -the properties desired and thereafter cooling to obtain substantially this structure at room temperature.

5. The process of treating those copper alloys Whose composition is such that-the particular alloy beingtreated falls within that portion of the temperaturc-composition diagram of its system which resembles the portion of the copper-zinc temperaturecompo'sition diagram in which 60-40 brass is found, which comprises heating the piece above the critical temperature to obtain substantially a single solid solution; quenching quickly to obtain substantially a single solid solution at room temperature; reheating the piece according to a predetermined schedule in order to obtain predetermined physical properties; and thereafter cooling to obtain substantially the structure corresponding thereto at room temperature.

6. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found, which comprises heating the piece above the critical temperature to obtain substantially a single solid solution; quenching quickly to obtain substantially a single. solid solution at room temperature; reheating the piece according to a predetermined schedule in predetermined physical properties; and thereafter cooling to obtain substantially the structure corresponding thereto at room temperature. j

7. The process of treating! those copper alloys whose composition such that the particular alloy being treated falls within that portion of the temperature-composition diagram of its system which resembles the portion of the copper-zinc temperaturecomposition diagram in which 6040 brass is found, which comprises subjecting the alloy to a heat treatment above its critical temperature to obtain substantially a single solid solution; followed by quick quenching; .and then to a second heat treatment at a lower temperatu e, followed by cooling at a rate which wilt-give substantially the structure of the, reheating temperature at room temperatur 8. The process of treating brass whose composition is such that the articular alloy being treated falls within t at portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found, which comprises subjecting the alloy to a heat treatment above its critical temperature to obtain substa-ntially'a single solid solution, followed by quick quenching; and then to a second heat treatment at a lower temperature, followed by cooling at a rate which will give substantially the structure of the reheating temperature at room temperature.

9. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found, which comprises subjecting the alloy to a heat treatment above 775 C. to obtain substantially a single solid solution, followed by quick quenching; and thento a second heattreatment at a lower temperature, followed by cooling at a rate which will give substantially the structure of the reheating temperature at room temperature.

10. The process of treating copper alloys whose composition is such that the particular alloy being treated fallswit-hin that portion of the temperature-composition diagram of its system which resembles the portion of the copper-zinc temperaturecomposition diagram in which 60-40 brass is found and which alloy is made up of substantially a single solid solution which comprises heating the alloy at a temperature below the critical temperature to cause a crystalline transformation of the single solid solution into two solid solutions; and thereafter cooling to obtain substantially the structure corresponding to the reheating temperature at room temperature.

11. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found. and which alloy is made up of substantially a single solid solution, which comprises heatingthe alloy at a temperature below the critical temperature to cause crystalline transformation of the single solid solution into two solid solutions; and thereafter cooling to obtain substantially the structure corresponding to the reheating temperature at room temperature.

12. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-Zinc temperature-composition diagram in which 60-40 brass is found, which comprises heating the alloy above the critiea ers cal temperature to form substantially a single solid solution; quenching quickly to obtain substantially'a single solid solution at room temperature; reheating at a tem-' perature between 400 C. and 750 (1.; and

being treated falls within that portion of.

the copperzinc temperature-composition diagram in which 60-40 brass is found, which comprises heating the alloy above the critical temperature to form substantially a single solid solution; quenching quickly to obtain.

substantially a single solid solution at room temperature; reheating at a temperature in the neighborhood of450 U; and thereafter cooling to obtain substantially the structure corresponding to that of the reheating temperature at room temperature, whereby an alloy of high ductility is obtained,

14. The process of treating brass Whose copper content is approximately 60%, which comprises heating the alloy above the critical temperature to form substantially a single solid solution; quenching quickly to obtain substantially a single solid solution at room temperature; reheating at a temperature between 400 C. and 750 (1; and thereafter quenching to obtain substantially the structure corresponding to that of the reheating temperature at room temperature, whereby an alloy of high tained. 4

15. The process of treating brass whose copper content is approximately 60%, which comprises heating the alloy above the critical temperature to form substantially a single solid solution; quenching quickly to obtain substantially a single solid solution at room temperature; reheating at a temperature in the neighborhood of 450 0.; and thereafter quenching to obtain substantially the structure corresponding to that of the reheating temperature at room temperature, wherebyan alloy of high ductility is obtained.

16. The process of treating brass whose copper content is approximately 60%, made up of substantially a single solid solution, which comprises heating the alloy at a temperature-between 400 G. and 750 (1; and thereafter cooling to obtain substantially the structure corresponding to the reheating temperature at .room temperature, whereby an alloy of high ductility is obtained.

ductility is ob 17. The process of treating brass whose copper content is approximately 60%, made up of substantially a single solid solution, which comprises heating the alloy to a temperature in the neighborhood of 450 t1; and thereafter cooling to obtain substantially the structure corresponding to the reheating temperature at room temperature, whereby an alloy of high ductility is obtained.

18. The process of treating those copper alloys whose composition is such that the particular alloy being treated falls within that portion of the temperature-composition diagram of its system which resembles the portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found, which comprises subjecting the alloy to a heat treatment above its critical temper ature to obtain substantially a single solid solution; quenching at a rate which will insure substantially a single solid solution at room temperature; and thereafter reheating the piece at a temperature below its critical temperature.

19.. The process of treating brass whose composition is such that the particular alloy being treated falls within that portion of the copper-zinc temperature-composition diagram in which 60-40 brass is found, which comprises subjecting the alloy to a heat treatment above its critical temperature to obtain substantially a single solid solution; quenching at a rate which will insure substantially a single solid solution at room temperature; and thereafter reheating the piece at a temperature below its critical ten1- perature. i

20, The process of treating brass whose copper content is approximately 60%, which comprises heating the alloy above the critical temperature to form substantially a single solid solution; quenching quickly to obtain substantially a single solid solution at room temperature; and thereafter reheating the piece at a temperature between 400 C. and 750 (1, whereby an alloy of high duetility is obtained.

21, The process of treating brass whose copper content is approximately 60%, which comprises heating the alloy above the critical temperature to form substantially a single solid solution; quenching quickly to obtain substantially a. single solid solution at room temperature; and thereafter reheating at a. temperature in the neighborhood of 450 O'., whereby an alloy of high ductility is obtained.

VICTOR o. HOMERBERG. DEXTER N. SHAW. 

